This invention relates to a push-button type mechanical pencil, wherein an upper barrel member or a lower barrel member, both of which form a barrel, is turned to move a lead-extruding structure, which is held in the interior of the barrel, forward and backward in the axial direction, and thereby enable the length of the portion of a lead-protecting pipe which projects out of the front end of a metal tip to be finely regulated in accordance with the purpose of using the mechanical pencil.
A mechanical pencil is provided with a lead-protecting pipe in a metal tip for the purpose of preventing the portion of the lead which projects from the free end of the metal tip from being broken. It is known that there are two types of structures for attaching a lead-protecting pipe to a metal tip. In one of these structures, a lead-protecting pipe is completely fixed to a metal tip. In the other structure, a lead-protecting pipe is attached to a metal tip so that the lead-protecting pipe retracts into the metal tip as the lead is worn while the mechanical pencil is in use. When a mechanical pencil employing the former type of lead-protecting pipe is used for the drawing purpose, especially, for drawing a line by utilizing a rule, the thickness of the rule and the length of a projecting portion of the lead-protecting pipe do not agree with each other, and it is difficult to draw a stable line.
When a mechanical pencil employing the latter type of lead-protecting pipe is used, the lead-protecting pipe moves freely in the backward direction while letters are written therewith, so that the mechanical pencil cannot be kept stable while in use. Therefore, a mechanical pencil employing this type of lead-protecting pipe is not suitable to be used for drawing which demands a high accuracy, whatever may be the case where it is used for general writing purposes. The lead-protecting pipe projects to a maximal extent whenever it is moved forward. Hence, especially, a lead-protecting pipe completely fixed to a metal tip is apt to damage the interior of a pocket or cause an accident. A lead-protecting pipe does not always require to be projected to a maximal extent when the mechanical pencil is used for writing ordinary letters, and the users have different favorite projection lengths of the lead-protecting pipe. Therefore, it is desirable that the projection length of a lead-protecting pipe be set optimumly in accordance with the use of the mechanical pencil and the taste of the users. However, as referred to above, the lead-protecting pipe in a conventional mechanical pencil is always projected to a maximal extent when the pencil is used. Consequently, it often occurs that a mechanical pencil cannot be used suitably for a certain purpose or in a desired manner due to the lead-protecting pipe of an unnecessarily large projection length.